24 ANNUAL OF SCIENTIFIC DISCOVERY. 



diamctor?, to the dlflorcnt lengths of tlic two rails on which they 

 were runniiiL!:. Tiiis, however, is not the case in practice, as any 

 one will find upon carcrully investigating the matter, inasmuch 

 as, in a vchicU' passing round a curve, the llange oF the off fore 

 whei'l will be found close up to the outer rail, while that of the 

 aft near winnd will be found running with its llange close up to 

 the inner one, so that no benelit whatever accrues from the use 

 of the cone, even in going round curves. 



" The question of passing with steadiness over straight line 

 seems to have been altogether overlooked in the introduction (-i 

 coned wheels, for it will be obvious that with the inch * play' 

 allowed between the tires and the rails, unless one-half of such 

 play be constantly [)reserved on c^ach sid(^ of the way, two wheels 

 staked upon the same axle will be running upon diHerent diame- 

 ters, and, consequently, a struggle arises wliich cannot fail to 

 result in oscillation, inasmuch as the moment one of the llanges 

 touches a rail, that wluMd, i)ecoming larircr than the opposite one, 

 turns it otf from the rail, only to make the opi)osite one perform, 

 in its turn, the same operation, wdien serious oscillation is the re- 

 sult. 



" As I have already stated, no advantage is found to arise in 

 the use of conical wiiccls in passing round curves, and as mucli 

 evil results therefrom, on straight lines, 1 have constructed up- 

 ward of 250 miles of railway aijroad, in the rolling stock of which 

 I have (le])arted from the usual form of wheel, and have used 

 only cylindrical ones, and have, as I expected, been gratified 

 with the satisfactory reports 1 have received of the steadiness oi 

 trains supplied with them. 



"Now that main-line companies are running their express 

 trains at such high velocities, this oscillation is becoming a very 

 serious matter, not only as a questit)n of safety, but also one of 

 * great discomfort to the passengers, to say nothing of the enor- 

 mous cost occasioned by this destructive action. I would, there- 

 fore, venture to recommend, that should any one desire to test the 

 correctness of the principles here stated, he should select a car- 

 riage known to be most subject to oscillation, and place under it 

 4 cvlindiical instead of conical wheels, and let this carriage 

 vuu in an exjiress train, care being taken to avoid the oscillation 

 of the two adjoining carriages with conical wheels being commu- 

 nicated to it, which would be effected by tlie introduction of two 

 coupling links, say 10 feet long, instead of the shorter ones in 

 general use, and he will at once perceive the advantage of using 

 cylindrical wheels." 



TUE USE OF COUNTEK-PRESSURE STEAM IN TUE LOCOMOTIVE 



ENGINE AS A BKAKE. 



M. L. De Chatclier gives the history of the improvement as fol- 

 lows : — 



*' About the middle of I860, when first I thought of organizing a 

 system of exi)eriments for removing the difficulties of reversing 

 the t-tcam, 1 began by trying whether it would be possible to 



